The present invention relates to a manufacturing system for forming a corrugated board of plural layers by laminating a plurality of corrugated core boards between a pair of liners.
Recently, as a corrugated board improved in strength, there has been proposed a double-faced corrugated board having plural layers of core boards. More particularly, as shown in FIG. 7, a corrugated board S.sub.a is formed by laminating two corrugated core boards C.sub.1 and C.sub.2 equal in both pitch P.sub.0 and flute tip height H.sub.0 between a pair of liners upper and lower liners L.sub.1,L.sub.2.
As shown in FIG. 8, the corrugated board S.sub.a is manufactured by delivering the liner L.sub.1 from roll paper 102 loaded on a mill roll stand 101, applying glue to the core board C.sub.2 by means of a glue applicator roll 104 of a single facer 103, laminating the thus-glued core board to the core board C.sub.1 while passing a pressure roll 105, and then passing the thus-laminated core boards through a clearance between an upper roll 106 and a lower roll 107 meshing with each other to corrugate the core boards. The corrugated core boards C.sub.1 and C.sub.2 are then guided along the peripheral surface of the upper roll 106 and are applied with glue at their flute tips by means of a glue applicator roll 108, thereafter join to the liner L.sub.1 at the position between the upper roll 106 and a pressure roll 109, and are laminated to the liner by the application of appropriate amounts of heat and pressure to form a single-faced corrugated board S.sub.2. Thereafter, though not shown, a liner is laminated to the single-faced corrugated board S.sub.2 to form a double-faced corrugated board.
The corrugated board S.sub.a is thus formed by laminating two core boards C.sub.1 and C.sub.2 between a pair of upper and lower liners L.sub.1,L.sub.2 and is therefore improved in strength as compared with a corrugated board formed by laminating one core board between two liners. However, since both core boards C.sub.1 and C.sub.2 are equal in pitch P.sub.0 and flute tip height H.sub.0, the strength of the corrugated board S.sub.a may be insufficient in a certain use. In view of this point, as a corrugated board further improved in strength, there has been proposed a double-faced corrugated board having plural layers of core boards different in flute tip height. As shown in FIG. 9, the said corrugated board, indicated at S.sub.b, is formed by laminating two corrugated core boards C.sub.1 and C.sub.2 between a pair of upper and lower liners L.sub.1,L.sub.2, the core boards C.sub.1 and C.sub.2 being equal in pitch P.sub.0 but having different flute tip heights H.sub.1 and H.sub.2.
The corrugated board S.sub.b is manufactured in such a manner as shown in FIG. 10. That is, the liner L.sub.1 is delivered from roll paper 202 loaded on a mill roll stand 201, while the core board C.sub.1 is passed through a clearance between an upper roll 204 and a pressure roll 205 meshing with each other in a first single facer 203, whereby the core board C.sub.1 is formed into a corrugated shape of low flute tips. The corrugated core board C.sub.1 is then guided along the peripheral surface of the upper roll 204 and is applied with glue at its flute tips by means of a glue applicator roll 206. The thus-glued, corrugated core board C.sub.1 then joins to the liner L.sub.1 at the position between the upper roll 204 and a pressure roll 207, and both are laminated together by the application of appropriate amounts of heat and pressure to form a single-faced corrugated board S.sub.1. The single-faced corrugated board S.sub.1 is then fed to a single facer 208, while the core board C.sub.2 is passed through a clearance between an upper roll 209 and a lower roll 210 meshing with each other and is thereby formed into a corrugated shape of high flute tips.
While guided along the peripheral surface of the upper roll 209, the corrugated core board C.sub.2 is applied with glue at its flute tips by means of a glue applicator roll 211, then joins to the single-faced corrugated board S.sub.1 at the position between the upper roll 209 and a pressure roll 212 and is laminated to the core board C.sub.1 by the application of appropriate amounts of heat and pressure to form a single-faced corrugated board S.sub.2. Though not shown, a double-faced corrugated board is fabricated by laminating a liner to the single-faced corrugated board S.sub.2.
In the conventional system for manufacturing the corrugated board S.sub.b, the corrugated core board C.sub.1 is laminated in the first single facer 203 to the liner L.sub.1 which is traveling while maintaining a predetermined tension after delivery from the roll paper 202. However, after the single-faced corrugated board S.sub.1 has passed the first single facer 203, its tension drops or vanishes. Consequently, there arises the problem that when the core board C.sub.2 is laminated to the core board C.sub.1 of the single-faced corrugated board S.sub.1 in the second single facer 208, it is impossible to laminate both core boards properly because their corrugations are displaced from each other.
More particularly, in the single facer 203, as shown in FIG. 11, the corrugated core board C.sub.1 is laminated to the liner L.sub.1 while the liner is maintained at a predetermined tension, so the pitch of the core board C.sub.1 is P.sub.a and there are three flute tips for each predetermined length M.sub.1. On the other hand, after passing the first single facer 203, the tension of the single-faced corrugated board S.sub.1 drops or vanishes, so that the pitch P.sub.b of the core board C.sub.1 becomes smaller and there are four flute tips at the predetermined length M.sub.1 (three flute tips at a predetermined length M.sub.2). See FIG. 12. In the second single facer 208, therefore, it is difficult to laminate the core boards C.sub.1 and C.sub.2 of different flute tip pitches P, and thus it is impossible to form a proper single-faced corrugated board S.sub.2. As noted previously, if the core boards C.sub.1 and C.sub.2 are different in the flute tip pitch P from each other in the second single facer 208, there will occur a phase shift. In more particular terms, as shown in FIG. 13, if the flute tip pitch P.sub.2 of the core board C.sub.2 becomes larger than the flute tip pitch P.sub.1 of the core board C.sub.1, there occurs a phase shift of +.delta. and the corrugations of the core boards C.sub.1 and C.sub.2 are displaced from each other. Further, as shown in FIG. 14, if the flute tip pitch P.sub.2 of the core board C.sub.2 is smaller than the flute tip pitch P.sub.1 of the core board C.sub.1, there occurs a phase shift of -.delta. and the corrugations of the core boards C.sub.1 and C.sub.2 are displaced from each other. Thus, once there occurs a displacement in corrugation between the core boards C.sub.1 and C.sub.2 in the second single facer 208, it becomes difficult to laminate both core boards properly, thus resulting in that not only the primary function of the double-faced corrugated board having plural layers of core boards for attaining both buffering effect and enhancement of strength can no longer be exhibited but also the double-faced corrugated board becomes no longer useful as product.